Memory Mapped File Mutex Problem

i have 2 programs need communicate each other.  1 windows service (which runs constantly) , other wcf web api has short ttl.  dont think types of programs here make difference in trying do.

the first program windows service - running

mutex mutex;  memorymappedfile mmf;  int m_ioffset = 0;  int m_ilength = 255;  byte[] m_bybuffer;  bool mutexcreated;      private void form1_load(object sender, eventargs e)  {       mutex = new mutex(true, "mmf_ipc", out mutexcreated);       mmf = memorymappedfile.createoropen("testapplication", m_ilength);  }      private void button1_click(object sender, eventargs e)  {     m_bybuffer = new byte[m_ilength];     m_bybuffer = tobytes(textbox1.text);     using (var accessor = mmf.createviewaccessor(m_ioffset, m_bybuffer.length))     {         accessor.writearray<byte>(0, m_bybuffer, m_ioffset, m_bybuffer.length);      }      mutex.releasemutex();  }    private byte[] tobytes(string str)  {      byte[] bytes = new byte[str.length * sizeof(char)];      system.buffer.blockcopy(str.tochararray(), 0, bytes, 0, bytes.length);      return bytes;  }

the second program wcf api - incremental calls whenever user needs

int m_ioffset = 0;  int m_ilength = 255;    private void button1_click(object sender, eventargs e)  {     byte[] buffer = new byte[m_ilength];     using (var mmf = memorymappedfile.openexisting("testapplication"))     {         using (var accessor = mmf.createviewaccessor(m_ioffset, buffer.length))         {              mutex mutex = mutex.openexisting("mmf_ipc");              mutex.waitone();              accessor.readarray<byte>(0, buffer, 0, buffer.length);         }      }      string str = system.text.encoding.default.getstring(buffer);      messagebox.show(str);  }

they can communicate not reliable.

sometimes program hangs, "object synchronization method called unsynchronized block of code." on mutex.releasemutex();

what missing? (thanks in advance help!)

here's basic solution using semaphores (i tend prefer them on events in case):

class program {     static void main() {         var writer = new thread(writer);         var reader = new thread(reader);          writer.start();         reader.start();          console.readline();     }      static void writer() {         var mmf = memorymappedfile.createoropen("testapplication", 4096);         var view = mmf.createviewaccessor();          // semaphore used signal shared memory empty         var empty = new semaphore(1, 1, "mmf_empty");         // semaphore used signal shared memory full         var full = new semaphore(0, 1, "mmf_full");          var = 0;          while (true) {             var message = encoding.utf8.getbytes(string.format("message {0}", i++));              // wait shared memory empty             empty.waitone();              // write length of message , message             view.write(0, message.length);             view.writearray(4, message, 0, message.length);              // signal reader have placed message in shared memory             full.release();         }     }      static void reader() {         var mmf = memorymappedfile.createoropen("testapplication", 4096);         var view = mmf.createviewaccessor();          var empty = new semaphore(1, 1, "mmf_empty");         var full = new semaphore(0, 1, "mmf_full");          var buffer = new byte[1024];          while (true) {             // wait message placed in shared memory             full.waitone();              // read message             int length = view.readint32(0);             view.readarray(4, buffer, 0, length);              // signal writer can place message in shared memory             empty.release();              console.writeline(encoding.utf8.getstring(buffer, 0, length));              thread.sleep(100);         }     } } 

i'm using 2 threads in same process sake of simplicity should work processes. note allows 1 message put in shared memory @ time. allow more messages need keep track of write offset , read offset (both stored in shared memory), allows create circular buffer. if need multiple reader/writer threads you'll need additional synchronization (in form of mutex or perhaps interlocked operations) prevent multiple readers/writers modifying shared memory @ same time.

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